1. Field of the Invention
The invention relates generally to animal litters and particularly to extruded animal litters having improved physical, functional, and related properties.
2. Description of Related Art
Conventional clay-based compositions used as animal litters represent a significant portion of the animal litter market, e.g., litter for cats, dogs, rabbits, gerbils, and other small animals. However, the relatively high density of clay used to produce the litters make the litters heavy and awkward to handle and transport, particularly in the large quantities. In addition, clay litters are not readily biodegradable and are prone to produce dust that contaminates the environment, particularly when tracked from a lifter box, by an animal using the litters. These conventional clay-based animal litters are typically made from non-swelling clays, swelling clays, or combinations thereof and are sold in the form of non-clumping litters and clumping litters.
Non-clumping animal litters are typically made by formulating non-swelling clays into animal litter particles. Such litters and methods for making such litters are known in the art. U.S. Pat. No. 4,949,672 discloses boron-based odor control animal litters comprising clay with absorbed solution of boron compounds in an aqueous alkali metal hydroxide. U.S. Pat. No. 7,228,819 discloses magnetically-attractable non-clumping animal litters comprising non-clumping absorbent particulate material and magnetically attractable metal particles bound together. U.S. Pat. No. 7,316,201 discloses a non-clumping animal litter that contains absorbent fibers, zeolite, mineral fillers, and binders. Non-clumping liters made from non-clay materials are also known e.g., U.S. Pat. No. 6,276,300 discloses animal litters comprising paper, sphagnum moss, zeolite molecular sieve and optionally sawdust. Many such litters are known in the art.
Clumping animal litters are typically made by coating a non-swelling clay or other material with a swelling clay such as bentonite, e.g., a non-swelling clay or agglomerated non-swelling clay particles (clay fines) coated with bentonite. Such litters and methods for making such litters are known in the art. U.S. Pat. No. 6,887,570 discloses coated clumping litter particles useful for the control and removal of animal waste. In one embodiment, the particles comprise non-swelling clay particles with swelling clay particles coated onto the non-swelling particles. U.S. Pat. No. 7,429,421 discloses coated clumping litter comprising non-swelling particles. U.S. Pat. No. 7,331,309 discloses clumping animal litters that forms solid clumps upon contact with aqueous solution. The litter contains an absorbent polymer and a gum and grist that form a homogenous mixture in which hydration with aqueous solution forms instantaneous clumps.
Additionally, animal litters made by processes that involve extrusion are known in the art. U.S. Pat. No. 3,923,005 discloses an animal litter comprising alfalfa and starch that is made using an extrusion process. U.S. Pat. No. 4,206,718 discloses a process for producing light weight animal litter from ground alfalfa and gelatinisable flour or starch. In one embodiment, the litters contain up to 10% bentonite as a binder. U.S. Pat. Nos. 5,452,684 and 5,577,463 disclose an animal litter comprising an extruded smectite clay that forms stronger clumps when wetted with animal urine. U.S. Pat. No. 7,603,964 discloses mixing a clay materials and a light-weighting material and forming the mixture into a composite particle using various methods such as agglomeration, compaction, and extrusion. WO2009133212A1 discloses methods for producing low-density agglomerated pet litters using minerals with an attapulgite content greater than 50% and an extrusion process.
Generally, all these litters function for their intended purpose, e.g., managing animal urine and feces. Further, the litters may, in some circumstances, be used for other purposes, e.g., absorbing environmental contaminants. However, as stated, these litters are made mostly from dense clays that are relatively difficult and expensive to handle and transport. Additionally, these litters are often inadequate for some functions, e.g., dust control. Therefore, there is a need for new litters and methods for making new litters that have improved physical, functional, and related properties, e.g., animal litters that are easier and less expensive for the manufacturer and the consumer to handle and transport.